In the fabrication of structural parts made of preimpregnated composite material, the material is assembled into a layup of plies (laminate), i.e., layers of the material, to the desired thickness, with each ply having the shape of the desired structural part, or another generalized shape which can be modified in a tool to the desired shape of the structural part. In either case, the layup is then cured in a tool to form the structural part.
A typical layup of preimpregnated composite material may include several types of preimpregnated composite material and any number of plies. For example, a layup comprising ten plies formed of the types of material noted below will be considered for discussion:
______________________________________ Ply Material Type ______________________________________ 1 bias-Ply 2 uni 3 uni 4 woven 5 woven 6 bias-Ply 7 bias-Ply 8 uni 9 uni 10 woven ______________________________________
The various material types are well known in the art. The bias-ply designation indicates that at least some of the filaments in the resin matrix are directed at any angle to the longitudinal axis of the material; the uni designation indicates that all the filaments in the resin matrix are directed parallel to each other and in the direction of the longitudinal axis of the material; and the woven designation indicates a combination of uni and 90.degree. bias filaments in the resin matrix. Other types of preimpregnated materials are available. However, the discussion here will be confined to the three noted types.
A ten ply layup then includes ply 1 as its top layer and ply 10 as its bottom layer. The formation of such a layup can be very labor intensive and consequently quite costly. For this reason, attempts at automation have been made. One attempt utilizes a Gerber cutting system with which a large number of plies can be cut and shaped. Still, the cutting, picking and kitting of preimpregnated composite material, especially of more than one thickness, on a Gerber cutting system continues to be a major production restraint, and continues to be relatively labor intensive. Several of the problem areas result from the heat generated by the reciprocating knife which fuses the edges of the plies together thereby preventing individual ply separation, and the provision of individual plies of various styles/types of materials which cannot be accomplished without an excessive machine loading and unloading time.
It would therefore be desirable to have an autonomous cutting, picking and kitting system and method which will produce a complete layup when needed with the plies arranged in proper sequence, i.e., in view of the example above, with bias-ply, uni, uni, woven, woven, bias-ply, bias-ply, uni, uni and woven plies.